Caffeine is not the diuretic demon
people are often told to avoid during exercise or while working in
extreme environmental conditions.

In fact, caffeine is no more a
diuretic than water, according to a research review article by
Larry Armstrong, a professor of exercise and environmental
physiology at the Neag School of Education.

For decades, health and exercise
experts have warned that consuming caffeine and caffeinated
beverages can lead to dehydration. But Armstrong, an avid runner
and a well respected scientist in the fields of thermo-regulation
and human performance, observed evidence to the contrary, so he
investigated whether abstaining from caffeinated beverages was
scientifically and physiologically justifiable.

"While there have been several
studies done that show caffeine is a mild diuretic, there is no
evidence that exercise, when combined with the consumption of
caffeine or caffeinated beverages, will result in chronic
dehydration, and this is contrary to the advice of most exercise
physiologists, physicians and dieticians," explains Armstrong,
who has been conducting fluid balance research since
1980.

"Therefore, the health and
performance of athletes and recreational enthusiasts will not be
impaired if they consume caffeine and caffeinated beverages in
moderation and eat a well-balanced diet," he says. The
National Coffee Association funded his study.

Among his findings:

When caffeine or a caffeinated
beverage is consumed, the body retains some of the fluid;

Caffeine consumption causes a mild
diuresis very similar to that of water (water, when consumed in
large volume, increases urine output);

There is no evidence that
consumption of caffeinated beverages causes a fluid-electrolyte
imbalance that is detrimental to health or exercise
performance;

A person who regularly consumes
caffeine has a higher tolerance to the diuretic effect;

The determination of safety or risk
of consuming caffeine and caffeinated beverages depends on several
factors, including the amount consumed and tolerance to
caffeine.

For decades, caffeine has been a
favorite stimulant for athletes trying to make weight or enhance
muscle definition before competition. Both the National Collegiate
Athletic Association (NCAA) and the International Olympic Committee
classify caffeine as a banned substance, because of its ergogenic
properties. But while there are instances of abnormal and unhealthy
diuretic use by athletes, Armstrong reports that "these
examples should not be interpreted to mean that the average person
who participates in exercise several times a week would be
jeopardizing his or her health by consuming one or two caffeinated
products each day."

Because the scientific literature
analyzed by Armstrong focused on moderate amounts of caffeine (one
to four cups of coffee a day), he advises that further research be
conducted to determine if chronic, high-dose caffeine consumed over
several days results in fluid-electrolyte imbalances.

His findings were published in the
June issue of the International Journal of Sport Nutrition and
Exercise Metabolism and were recently presented at the
American College of Sports Medicine conference in St. Louis,
Missouri.